1. Field of the Invention
This invention is in the field of heat-recoverable articles having an outer layer which is thermoplastically deformable, and an inner layer of a material which has elastic memory and is therefore heat recoverable.
2. Description of the Prior Art
A laminated article consisting of an outer layer which is dimensionally stable but thermoplastically deformable and an inner cross-linked, heat-recoverable layer is described in DE OS No. 23 44 086 (corresponding to U.S. Pat. No. 4,035,534). In the use of such shrinkable articles, it is common practice to indicate the existence of a specific softening temperature by means of so-called color indicators, also known as thermocolors. These color indicators produce a change in color at a specific temperature, for example, 130.degree. C. thereby indicating to the user that the temperature required for back-shrinkage has been reached. The addition of such color indicators, however, requires an additional expense and it is likewise not always possible to find precisely matching indicators for specific temperature values in an appropriately fine graduation. Another disadvantage stems from the fact that the color indicators only indicate the surface temperature, and where the article is relatively thick or consists of multiple plies, the surface temperature can vary considerably compared from temperatures in the internal portions.